Chronic ethanol downregulates PKA activation and ciliary beating in bovinebronchial epithelial cells

Previously, we reported that ethanol (EtOH) stimulates a rapid increase in ciliary beat frequency (CBF) of bovine bronchial epithelial cells (BBEC). A gents activating cAMP-dependent protein kinase (PKA) also stimulate CBF. Et OH stimulates BBEC CBF through cyclic nucleotide kinase activation. However , EtOH-stimulated CBF is maximal by 1 h and subsides by 6 h, returning to b aseline by 24 h. We hypothesized that the loss of EtOH-stimulated CBF was a result of downregulation of PKA activity. To determine the PKA activation state in response to EtOH, ciliated BBEC were stimulated for 0-72 h with va rious concentrations of EtOH and assayed for PKA. EtOH (100 mM) treatment o f the cells for 1 h increased PKA activity threefold over unstimulated cont rols. PKA activity decreased with increasing time from 6 to 24 h. When BBEC were preincubated with 100 mM EtOH for 24 h, the stimulation of PKA by iso proterenol or 8-bromo-cAMP was abrogated. EtOH desensitizes BBEC to PKA-act ivating agents, suggesting that EtOH rapidly stimulates, whereas long-term EtOH downregulates, CBF via PKA in BBEC.